The present invention is directed to apparatus for uniformly applying either liquid or foam compositions to a moving web.
In copending U.S. patent application Ser. No. 390,114, filed on June 18, 1982, now U.S. Pat. No. 4,398,665, there is disclosed an arrangement for applying either liquids or foam to a moving web. That invention provides a trough into which the liquid or foam is directed. A curved blade is located on the opposite side of the trough. When the trough fills, the excess fluid flows over the crest of the blade and is uniformly deposited onto the web as it passes by the edge of the blade.
The arrangement described in Ser. No. 390,114 is particularly suited for use in applications such as dyeing wide lengths of carpet which require a substantial volume of liquid or foam to be available. The presence of a trough for the fluid material is desirable for such an application. On the other hand, when foam is the material being handled, an important consideration is its stability, i.e., its resistance to breakdown into liquid and air.
The stability of a foam is significantly affected by its age. While some foams are relatively stable, many others break down in very short periods of time. Accordingly, it is an objective of the present invention to provide an apparatus which can apply a foam to a moving web with minimum foam ageing and breakdown problems.
In U.S. Pat. No. 4,292,918 granted on Oct. 6, 1981, an apparatus is disclosed for applying liquid chemicals to a moving web in which a manifold covered with a sheath of porous material is positioned such that the sheath engages a curved blade. Liquid supplied to the manifold passes through the sheath and is directed onto the blade so as to flow as a film along the blade's surface and be deposited onto a web of material moving past an edge of the blade.
The apparatus disclosed in U.S. Pat. No. 4,292,918 is not suitable for applying foam to a web, however. This is because the porous sheath surrounding the manifold would prevent the foam from reaching the blade. Even if the porous sheath were not present, the particular arrangement by which fluid is directed to the manifold in U.S. Pat. No. 4,292,918 would fail to produce uniform distribution if foam were the fluid used. Such non-uniformity would cause the foam to unevenly age and break down. Furthermore, a uniform film of foam would not be obtained on the curved blade.